A 42 year-old male presented with a history of right renal agenesis and kidney transplantation 6 years ago due to end-stage renal failure. Left kidney biopsy revealed chronic nephropathy secondary to focal segmental glomerulosclerosis.
The patient presented with fever and increased inflammatory parameters and therefore an US and CT were performed.
The ultrasound revealed the absence of the right kidney in its usual location. Inferiorly to the bladder an anechoic rounded image with a defined wall was seen in the location of the right seminal vesicle measuring 3.8 cm, associated with bilateral dilated seminal vesicles.
CT also revealed a hypodense rounded mass in the right seminal vesical with defined wall without contrast enhancement, dilation of seminal vesicles, and absence of the right kidney. The left kidney showed decreased size and the transplanted kidney was seen in the right iliac fossa.
Cystic masses in the seminal vesicles may be either acquired or congenital. Acquired cysts are most commonly bilateral and present in elder patients. Congenital cysts, usually unilateral, become apparent in the second or third decade of life, coincidental with the period of greatest sexual activity. Atresia of the ejaculatory ducts causes accumulation of secretions, dilation and cyst formation in the seminal vesicles. Congenital cysts are associated with ipsilateral renal agenesis duct in two-thirds of cases . This is explained by embryological maldevelopment of the mesonephric or Wolffian duct believed to occur between the 4th and 7th week of gestation. Absent ureter, hemitrigone or testicular ectopia might also be present. The triad consisting of ejaculatory duct obstruction, seminal vesicle cyst and ipsilateral renal agenesis is designated as Zinner syndrome.
Their clinical presentation ranges from asymptomatic in cysts smaller than 5cm to bladder irritation, pelvic pain or discomfort, ejaculatory pain, dysuria, frequency, hematuria and urinary infections. Infertility, hematospermia and enuresis may also result. Cysts greater than 12cm (giant cysts) usually result in symptoms due to mass effect, such as bladder or colonic obstruction. Rarely, malignant transformation in the seminal vesicle cyst may occur .
Initial diagnostic should include abdominal or transrectal ultrasound. Ultrasonographic findings include an anechoic mass in the dependence of the seminal vesicle with a thick irregular wall that can show mural calcification. Internal debris can be seen if there was prior haemorrhage or infection. Sectional studies might then be indicated for further evaluation and detection of accompanying deformities. CT can reveal a retrovesicular mass just above the prostate gland showing attenuation similar to water and a thick and irregular wall. Ipsilateral enlargement of the seminal vesicle might also be seen. MRI is considered the best imaging study in the evaluation of malformations of the mesonephric duct due to its multiplanar ability, excellent soft tissue resolution and the use of non-ionising radiation . MR imaging shows low T1-weighted and high T2-weighted signal intensity, characteristic of cystic masses. With infection or haemorrhage a T1-weighted and T2-weighted signal intensity may be seen . After intravenous contrast there is enhancement of the cyst wall but not its content.
Treatment of the seminal vesicle cyst will depend on the existence of symptoms. Treatment modalities include medical treatment, percutaneous drainage, transurethral aspiration and alcohol injection, transrectal aspiration, laparoscopy or even open surgery 
Differential Diagnosis List
Ejaculatory duct cyst
Mullerian duct cyst